It is known in the art to fabricate generally planar display devices which include an image sheet and a lenticular lens sheet which, in combination, give the image and appearance of three dimensionality. The lenticular lens sheet and the image sheet must be aligned properly to avoid a distorted image. The components have heretofore been in sheet form because the process of combining them is usually manual to ensure necessary registration.
The illusion of three dimensionality requires the image originally be made with a special three dimensional or stereoscopic camera, photographing the desired object from a plurality of angularly displaced positions. Such a camera typically uses a photosensitive film disposed behind a lenticular screen. The lenticular screen is positioned adjacent the photosensitive film so the focal point of each lenticule generally coincides with the front surface of the film. Thus, the image of the object is focused into a narrow image band which is exposed in the film. As the camera is shifted to the next angular position, the lenticular screen is also shifted slightly. A subsequent picture image of the object from the new angular position is then exposed into a separate image band in the film adjacent the preceding image band. Each time the camera is moved to a new angular position, the object is photographed and the image is exposed in the film as a similar, narrow image band adjacent the previously formed image band, until a series of image bands representing different views of the object is created. To avoid overlap of image bands, the lenticular screen is only moved a distance equal to the width of a single lenticule as the camera is moved through its full angular range. This collection of image bands, which is formed under a single lenticule, may be called an image element. Each image element is approximately the width of a single lenticule and includes all of the condensed views of the object.
Cameras of this type are disclosed in Stockbridge et al., U.S. Pat. No. 3,380,360, issued Apr. 30, 1968 and Bonnet, U.S. Pat. No. 2,508,487, issued May 23, 1950. Both of those patents disclose three dimensional or stereoscopic cameras used to photograph objects from numerous angular positions where the photograph taken at each position is exposed on a film as a linear image band.
Once the object is photographed from the various positions, the film may be developed the same as any other photographic film, but the resulting image is a compilation of the numerous adjacent image bands. Each image band represents the object from a given angle, albeit in a focused or compressed form. This can provide the overall image with a somewhat distorted look to the naked human eye. However, when the developed image is combined with a lenticular screen or sheet having lenticules of approximately the same size and focal length as the lenticular sheet used to expose the film, the image becomes clear to the human eye as viewed through the screen.
The lenticular sheet must be placed over the image elements so the focal point of each lenticular lens coincides with the front surface of the image sheet. The image will appear to be three-dimensional because the observer is viewing the image through the lenticular sheet from a slightly different angle due to the lateral spacing between his eyes. In effect, this allows each eye to focus on a different image band representing different views of the photographed object from separate angles, thereby giving the viewer the illusion of a three dimensional image.
In the past, the lenticules and image elements were relatively wide and each lenticule and to be perfectly aligned over each image element to obtain a clearly defined three dimensional image. It has been difficult to obtain precise alignment and impossible to mass produce three dimensional images efficiently and economically. Typically, the lenticular sheet has been manually positioned over the image sheet and then carefully adjusted to eliminate moire line or interference. This is a time consuming, inefficient and expensive task.
Further difficulties exist in mass producing three dimensional sheets for use in publications such as magazines due to the size of the lenticules and the consequent thickness of the lenticular lens sheet. However, larger lenticules have longer focal lengths and necessitate a thicker lens overlay so the focal point of the lenticule is approximately adjacent the image elements on the image sheet. This, of course, leads to a relatively thick composite sheet which is not suitable for magazines or other printed media that require a thinner sheet dimension. Making the sheet sufficiently thin to be used in magazines requires the lenticules to be extremely small thus making it more difficult to form the lenticular lens sheet and properly align it with the image sheet. The required precision has made the use of efficient, high output machinery difficult.
It has long been desirable but unattainable to make both the image sheet and the lenticular lens sheet in continuous form and then combine them at a rapid pace with precise registry to produce a finished product having photographically acceptable quality. Standard printing methods could then be used to reproduce the images in continuous form. Though techniques have been developed for creating a lenticular lens in continuous form, and certain methods and devices have also been used in an attempt to combine an image web with a continuous lenticular lens, none of these devices is able to produce a thin, flexible lenticular image composite for economical use in the production of, for example, magazines while maintaining the precision necessary to produce quality images having the illusion of three dimensionality without interference lines or distorted appearance.
In three patents to Conley, U.S. Pat. No. 4,420,502, issued Dec. 13, 1983, U.S. Pat. No. 4,414,316, issued Nov. 8, 1983, and U.S. Pat. No. 4,420,527, issued Dec. 13, 1983 an apparatus and method for making a composite sheet material are disclosed. A transparent base web is directed onto the surface of a first roll and advanced along an arcuate path around the first roll and then through a narrow gap disposed between the first roll and a second roll. Before the transparent base web passes between the first and second rolls, a flowable, uncured actinic radiation-curable thermosetting resin is directed onto the web behind the narrow gap. The second roll includes grooves so that, as the resin covered web passes through the narrow gap and around the second roll, lenticular formations are made in the flowable resin. Ultraviolet radiation is directed through the transparent base web and into the flowable resin layer while it remains in contact with the second roll. Thus, the flowable resin is cured into a composite lenticular lens sheet.
Such a process can produce small, well defined lenticular lenses. However, the difficulty remains in properly joining such a lenticular lens with a corresponding image web in a manner that avoids distortion of the image. Typically, the lenticular lens will still need to be cut in sheets and then carefully aligned by hand with a corresponding image sheet. It would be advantageous, and meet the long-felt need summarized above, if such a lenticular lens could be precisely aligned and combined with the corresponding images while the image sheet and the lenticular lens both remained in continuous form. This would greatly increase the efficiency and volume of the finished web resulting in a very economical product.
Other patents disclose methods and devices for making lenticular lens products but none with the accuracy or precision that would allow the finished product to be used in typical publications such as magazines. For instance, Jerothe et al., U.S. Pat. No. 3,264,164, issued Aug. 2, 1966, discloses a device which makes a laminated, flexible fabric-like material having interesting characteristics of color and depth. However, precise accuracy is not necessary since one of the purposes of the patented device is to produce images having a moire effect. Additionally, that approach uses colored lines and various colored shapes placed at different depths between cumulative flexible sheets. In the Jerothe et al. device, a relatively thick sheet is used for the formation of the lenticular lens. The lenticular lens sheet is laminated with various films and the resulting laminate passes between a pressure roll and a gravure roll where surface ribs or lenticular lens type ribs are formed by pressing the relatively thick lens forming sheet against the gravure roll. That device, however, cannot be accurately controlled to make extremely small accurate lenses in alignment with the image bands of an image web to yield photographically acceptable image quality.
Leach, U.S. Pat. No. 3,565,733, issued Feb. 23, 1971 discloses an apparatus for making a composite web from paper web combined with melted plastic. In Leach, a paper web, which can include an image, is passed between a pressure roll and a coating roll and then around a chilled embossing cylinder. A melted plastic is poured onto the coating roll which brings the melted plastic into contact with the paper web. This combined paper web and melted plastic is immediately brought into contact with the surface of the chilled embossing cylinder which solidifies the melted plastic leaving lenticular lens-type formations in plastic. A problem with the Leach apparatus is that it does not provide for the precision alignment of the lenticular lens formations with the image elements on the image web. This prevents the constant replication of high quality images having the appearance of three dimensionality without distortion. Additionally, meltable plastic will not retain its proper shape under the rigors of magazine use and shipping which can tend to place the lenticular lens formations under harsh conditions of pressure and heat. Once the lenticular lenses degrade, the three dimensional effect is lost. See also U.S. Pat. No. 3,607,340 to Stroupe issued Sep. 21, 1971.
In Lemelson, U.S. Pat. No. 3,146,492, issued Sep. 1, 1964, an apparatus is disclosed which produces a multiple image sheet display on a continuous basis. In Lemelson, an impressionable sheet is laminated with a plurality of sheets and then passed through a pair of rolls. One of the rolls is an embossing roll which creates lenticular formations in a face of the impressionable sheet. The apparatus is similar to those mentioned above in that it is difficult to form precision lenticules in the solid web without which an image of photographically acceptable quality cannot be reliable and repeatedly reproduced. Additionally, there is no way for the machine to provide precise alignment of the image elements with the lenticules.
The present invention addresses the foregoing drawbacks involved in making a precision lenticular lens image web having three dimensional image characteristics with photographic quality.